The "Finger-four" formation (also known as the "four finger formation"), is a flight formation used by fighter aircraft. It consists of four aircraft, and four of these formations can be combined into a squadron formation.
The formation consists of a flight of four aircraft, composed of a "lead element" and a "second element", each of two aircraft. When viewing the formation from above, the positions of the planes resemble the tips of the four fingers of a human right hand (without the thumb), giving the formation its name.
The lead element is made up of the flight leader at the very front of the formation and one wingman to his rear left. The second element is made up of an additional two planes, the element leader and his wingman. The element leader is to the right and rear of the flight leader, followed by the element wingman to his right and rear.
Both the flight leader and element leader have offensive roles, in that they are the ones to open fire on enemy aircraft while the flight remains intact. Their wingmen have a defensive role — the flight wingman covers the rear of the second element and the element wingman covers the rear of the element lead.
Four of these flights can be assembled to form a squadron formation which consists of two staggered lines of fighters, one in front of the other. Each flight is usually designated by a color (i.e. Red, Blue, Yellow, and Green).
The formation was developed by several air forces independently in the 1930s. The Finnish Air Force adopted it during 1934-1935.  Luftwaffe pilots developed the formation independently in 1938 during the Spanish Civil War, and were the first to use it in combat.
Most notable in its development and use in the Luftwaffe were Günther Lützow and Werner Mölders and their fellow airmen. In the German Luftwaffe the flight (German: Schwarm) was made up of two pairs (German: Rotte) of aircraft. Each Rotte was composed of a leader and a wingman. The aircraft in the Schwarm had greater vertical and horizontal separation, so they were free to scan in all directions for enemy aircraft rather than focusing on maintaining a close formation. This allowed the pilots to maintain greater situational awareness and reduce the chance of being spotted by the enemy due to the looser formation. The two Rotten could split up at any time and attack on their own. The Rottenführer (pair leader) would attack enemy aircraft, leaving his wingman to scan for threats and protect him while he engaged the enemy. The Finnish Air Force's approach was even more flexible by allowing the pilot who spotted the enemy to become the leader of the pair or even the whole flight for the duration of the attack as he had the best situational awareness at that moment in time.
The Luftwaffe continued the use of this formation during the Battle of Britain, in which its effectiveness was shown to be considerably greater than the standard three-aircraft "Vic" close formation used by the Royal Air Force (RAF). The RAF and later the United States Army Air Forces (USAAF) and Soviet Air Forces adopted this formation and used it themselves against the Luftwaffe. The Finnish Air Force proved the effectiveness by achieving a 16:1 kill ratio with the finger-four during the 1939-1940 Winter War against the Soviet Air Force, which at the time used the conventional Vic formation and superior aircraft.
The Soviet air force units in the Spanish Civil War adopted the formation against the Germans but reverted to the "V" on return to the Soviet Union. The flying ace Douglas Bader was the first RAF pilot to adopt the formation in 1940. The United States Army Air Corps and Naval Aviation began using a concept called "Fighting Pair" from 1940–41. Japan too adopted the finger-four formation during World War II.
Missing man formation
The finger-four formation became less common after World War II. However, it is still used in the "Missing Man Formation" at pilots' funeral ceremonies. The formation performs a fly-by in level flight over the funeral, at which point the second element leader climbs vertically and departs the formation, symbolizing the departure of the person being honored.
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